Featured Research

from universities, journals, and other organizations

Quantum engines must break down

Date:

June 26, 2013

Source:

University College London

Summary:

Our present understanding of thermodynamics is fundamentally incorrect if applied to small systems and need to be modified, according to new research. The work establishes new laws in the rapidly emerging field of quantum thermodynamics. The findings have wide applications in small systems, from nanoscale engines and quantum technologies, to biological motors and systems found in the body.

Share This

Our present understanding of thermodynamics is fundamentally incorrect if applied to small systems and needs to be modified, according to new research from University College London (UCL) and the University of Gdańsk. The work establishes new laws in the rapidly emerging field of quantum thermodynamics.

Related Articles

The findings, published today in Nature Communications, have wide applications in small systems, from nanoscale engines and quantum technologies, to biological motors and systems found in the body.

The laws of thermodynamics govern much of the world around us -- they tell us that a hot cup of tea in a cold room will cool down rather than heat up; they tell us that unless we are vigilant, our houses will become untidy rather than spontaneously tidy; they tell us how efficient the best heat engines can be.

The current laws of thermodynamics only apply to large objects, when many particles are involved. The laws of thermodynamics for smaller systems are not well understood but will have implications for the construction of molecular motors and quantum computers, and might even determine how efficient energy extracting processes such as photosynthesis can be.

In this study researchers used results from quantum information theory to adapt the laws of thermodynamics for small systems, such as microscopic motors, nanoscale devices and quantum technologies.

Small systems behave very differently to large systems composed of many particles. And when systems are very small, then quantum effects come into play. The researchers found a set of laws which determine what happens to such microscopic systems when we heat them up or cool them down. An important consequence of their laws is that there is more fundamental irreversibility in small systems, and this means that microscopic heat engines can not be as efficient as their larger counterparts.

"We see that nature imposes fundamental limitations to extracting energy from microscopic systems and heat engines. A quantum heat engine is not as efficient as a macroscopic one, and will sometimes fail," said Professor Oppenheim, a Royal Society University Research Fellow at UCL's Department of Physics and Astronomy and one of the authors of the research. "The limitations are due to both finite size effects, and to quantum effects."

The researchers investigated the efficiency of microscopic heat engines and found that one of the basic quantities in thermodynamics, the free energy, does not determine what can happen in small systems, and especially in quantum mechanical systems. Instead, several new free energies govern the behaviour of these microscopic systems.

In large systems, if you put pure energy into a system, then you can recover all this energy back to use to power an engine which can perform work (such as lifting a heavy weight). But the researchers found that this was not the case for microscopic systems. If you put work into a quantum system you generally cannot get it all back.

Professor Michal Horodecki of the University of Gdansk, and co-author of the paper, said: "Thermodynamics at the microscopic scale is fundamentally irreversible. This is dramatically different to larger systems where all thermodynamic processes can be made reversible if we change systems slowly enough."

More From ScienceDaily

More Matter & Energy News

Featured Research

Mar. 3, 2015 — By examining the forces that the segments of mosquito legs generate against a water surface, researchers have unraveled the mechanical logic that allows the mosquitoes to walk on water, which may ... full story

Mar. 3, 2015 — Researchers have developed a new way of rapidly screening yeasts that could help produce more sustainable biofuels. The new technique could also be a boon in the search for new ways of deriving ... full story

Mar. 3, 2015 — Major cities in the UK are falling behind their international counterparts in terms of their use of smart technologies, according to a new study. The research has found that smart cities in the UK, ... full story

Mar. 3, 2015 — Scientists have explored friction at the microscopic level. They discovered that the force generating friction is much stronger than previously thought. The discovery is an important step toward ... full story

Mar. 3, 2015 — Micro-drones are already being put to use in a large number of areas: These small aircraft face extensive requirements when performing aerial observation tasks or when deployed in the field of ... full story

Mar. 3, 2015 — Recent research contributes to the effort to determine the nature of dark matter, one of the most important mysteries in physics. As indirect evidence provided by its gravitational effects, dark ... full story

Mar. 3, 2015 — Physicists have shown for the first time that electrons in graphene can be moved along a predefined path. This movement occurs entirely without loss and could provide a basis for numerous ... full story

Mar. 3, 2015 — Magnetic vortex structures, so-called skyrmions, could in future store and process information very efficiently. They could also be the basis for high-frequency components. For the first time, a team ... full story

Featured Videos

Forensic Holodeck Creates 3D Crime Scenes

Reuters - Innovations Video Online (Mar. 3, 2015) — A holodeck is no longer the preserve of TV sci-fi classic Star Trek, thanks to researchers from the Institute of Forensic Medicine Zurich, who have created what they say is the first system in the world to visualise the 3D data of forensic scans. Jim Drury saw it in operation.
Video provided by Reuters

Solar Plane Passes New Test Ahead of World Tour

AFP (Mar. 2, 2015) — A solar-powered plane made a third successful test flight in the United Arab Emirates on Monday ahead of a planned round-the-world tour to promote alternative energy. Duration: 01:05
Video provided by AFP

Electric Hydrofoiling Watercraft Delivers Eco-Friendly Thrills

Reuters - Innovations Video Online (Mar. 2, 2015) — The Quadrofoil is a high-tech electric personal watercraft that its makers call a &apos;sports car for the water&apos;. When it hits 10 km/h, the Slovenian-engineered Quadrofoil is lifted above the water onto four wing-like hydrofoils where it &apos;flies&apos; above the surface with minimal water resistance. Matthew Stock reports.
Video provided by Reuters

Related Stories

Feb. 9, 2015 — New research has uncovered additional second laws of thermodynamics which complement the ordinary second law of thermodynamics, one of the most fundamental laws of nature. These new second laws are ... full story

Jan. 15, 2015 — Using the cadmium selenide quantum dot, researchers collaborated to understand how protein corona forms and what is different about the quantum dot before and after the formation of the ... full story

May 20, 2014 — A change of models demystifies anomalous particle behavior at very low temperatures, supporting that the third law of thermodynamics cannot be violated. In theory, the laws of physics are absolute. ... full story

May 5, 2011 — Researchers have used a quantum mechanical system in the laboratory to simulate complex many-body systems. This experiment promises future quantum simulators with enormous potential insights into ... full story

Nov. 30, 2010 — Researchers in Germany have successfully fabricated a rudimentary quantum computing hybrid system using electronic excitations in nano-diamonds as qubits and optical nanostructures, so-called ... full story

ScienceDaily features breaking news and videos about the latest discoveries in health, technology, the environment, and more -- from major news services and leading universities, scientific journals, and research organizations.